It’s not really that he’s controversial. There’s plenty of contrarians with even more offensive opinions.
It’s that as a person he is all round risible. He’s straight out of satire, presenting himself as this expert professor - on every field, no less - who is all seeing and all knowing and enjoys being the bastion of self help and self control in between bouts of benzo addiction, making himself sick on beef diets and randomly bursting into teas talking about benign subjects.
Anyone with half a brain watches two or three minutes of him, sees straight through his shtick and appreciates him as a comedy act while being utterly bemused at anyone who takes him seriously. It’s like a Sacha Baron Cohen character suddenly became a guru for millions of people while the rest of us live out the Anakin Skywalker meme template. He is some sort of performance art, right?
For me, and I think for a lot of other people, it's also due to the reaction he gets from his fans and people not familiar with him. He's a mess and a horrible person, but if he was ranting in a pub or on Youtube with a few thousand views, who cares, really.
He's the current prime example where his fans' most uttered phrase is "you're taking him out of context", and where they will deny things he's said either because of a combination of extreme confidence coupled with ignorance, or by twisting themselves into pretzels when evidence is staring them in the face. In the late noughties and early parts of last decade it used to be Sam Harris, now it's Jordan Peterson.
One example is that they'll strongly deny that he's right wing or conservative. They'll also use this claim as evidence that his critics are liars and smear merchants. They'll say he's a centrist, a classical liberal or non-political. They'll say he wants universal healthcare, forgetting that he's Canadian or being ignorant of the fact that in many countries most conservatives are. Meanwhile Peterson is preaching at PragerU, writing 12 rules for conservatives, and recently even directly endorsing a member of the Canadian Conservative Party as the next president.
Another example is that whole pronoun thing, where they say that his opposition is only the legal aspect of it; he is opposed to compelled speech by the government, he doesn't have anything against trans people and will use his students' preffered pronouns. And even though he did say those things, with the added caveat that he'll only respect trans students if they present acceptably as their professed gender, whatever that means, he'll also go on national TV and say that he will never use neopronouns, and that they/their as a gender neutral pronoun doesn't work, making it effectively impossible for him to use the preffered pronouns of non-binary people. He'll do newspaper interviews where he directly and purposefully misgender a non-binary colleague of his, and he'll go on Rex Murphy where they both purposefully misgender a trans woman because they think (probably correctly) that she's a bad person, thereby proving that it's not just the non-binary he has problems with. He'll also do interviews where he calls people identifying as a trans a psychological epidemic, and likens it to other crazes like hysteria in women or the multiple personality disorder part of schizofrenia that isn't real. Not exactly a hallmark of respect to say that trans people aren't actually trans.
There are plenty more examples, of course, this is just an illustration.
